Types of relays, classification of relays ,different type of relays, electomechanic relays

Types of Relays

Types of protection relays are mainly based on their characteristic, logic, on actuating parameter and operation mechanism.

Based on operation mechanism protection relay can be categorized as electro magnetic relay, static relay and mechanical relay. Actually relay is nothing but a combination of one or more open or closed contacts. These all or some specific contacts the relay change their state when actuating parameters are applied to the relay. That means open contacts become closed and closed contacts become open. In electromagnetic relay these closing and opening of relay contacts are done by electromagnetic action of a solenoid.

In mechanical relay these closing and opening of relay contacts are done by mechanical displacement of different gear level system.

In static relay it is mainly done by semiconductor switches like thyristor. In digital relay on and off state can be referred as 1 and 0 state.

Based on Characteristic the protection relay can be categorized as

1.Definitetimerelays

2.Inversetimerelayswithdefiniteminimumtime(IDMT)

3Instantaneousrelays

4.IDMTwithinst.

5.Steppedcharacteristic

6.Programmedswitches

7. Voltage restraint over current relay

Based on of logic the protection relay can be categorized as

1.Differential

2.Unbalance

3.Neutraldisplacement

4.Directional

5.Restrictedearthfault

6.Overfluxing

7.Distanceschemes

8.Busbarprotection

9.Reversepowerrelays

10.Lossofexcitation

11.Negative phase sequence relays etc.

Based on actuating parameter the protection relay can be categorized as

1.Currentrelays

2.Voltageelays

3.Frequencyrelays

4. Power relays etc.

Based on application the protection relay can be categorized as

1.Primaryrelay

2. Backup relay